Autoimmune blistering disease — GP recognition and urgent referral

Autoimmune blistering diseases (AIBDs) are a group of rare but serious dermatological conditions in which autoantibodies attack structural proteins in the skin, causing fluid-filled blisters and erosions. The general practice role is not to manage these conditions — that is specialist territory — but to recognise them early, initiate the correct diagnostic workup, review the medication list for drug triggers, and refer to dermatology with appropriate urgency. Missing bullous pemphigoid during its prodromal pruritic phase, or failing to act when flaccid oral erosions suggest pemphigus vulgaris, has real consequences. This article covers the four conditions GPs are most likely to encounter: bullous pemphigoid, pemphigus vulgaris, dermatitis herpetiformis, and drug-induced linear IgA disease.

A. Core clinical — the AU general-practice framework

Classification: subepidermal versus intraepidermal

The first clinically useful distinction is the level of the skin split.

Subepidermal split — tense bullae that do not rupture easily: bullous pemphigoid, pemphigoid gestationis (pregnancy-associated), mucous membrane pemphigoid (predominantly mucosal), linear IgA disease, dermatitis herpetiformis, and epidermolysis bullosa acquisita.

Intraepidermal split — fragile bullae that rupture rapidly leaving erosions: pemphigus vulgaris (desmoglein 3 ± 1), pemphigus foliaceus (desmoglein 1, superficial and scaly), and paraneoplastic pemphigus (malignancy-associated).

Drug-induced forms sit across both categories: DPP-4 inhibitors and PD-1 inhibitors → BP (subepidermal); vancomycin is the classic trigger for linear IgA disease (subepidermal).

Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) are drug-induced epidermal detachment emergencies and require immediate emergency department referral — they are not managed in general practice.

Bullous pemphigoid — the most common AIBD

Bullous pemphigoid is the most common autoimmune blistering disease, predominantly affecting adults over 70. Incidence rises with an ageing population.

Two phases distinguish its clinical course. The prodromal phase — lasting weeks to months — presents with intractable pruritus on normal-appearing or urticarial-looking skin. This is the phase most often misdiagnosed as eczema, contact dermatitis, or drug rash. The bullous phase then produces tense bullae on erythematous, urticarial, or normal skin, predominantly in flexural sites (groin, axillae, abdomen, inner thighs). Bullae are tense — the subepidermal split makes them robust. Nikolsky sign is negative. Mucous membrane involvement is uncommon (10–30%).

Drug triggers to review first: DPP-4 inhibitors (gliptins — sitagliptin, linagliptin, vildagliptin, saxagliptin) are now the most clinically relevant drug trigger in Australia. PD-1 and PD-L1 checkpoint inhibitors (pembrolizumab, nivolumab, atezolizumab) increasingly cause BP in oncology patients. Furosemide, spironolactone, and ACE inhibitors are less common triggers. Drug-induced BP usually resolves after the culprit is withdrawn.

Neurological association: BP is three times more common in patients with Alzheimer’s disease, Parkinson’s disease, stroke, and multiple sclerosis — the reason is not fully understood but may relate to desmoglein or BP180 antigen cross-reactivity with neuronal antigens.

Diagnosis: lesional skin H&E shows subepidermal split with eosinophilic infiltrate; perilesional direct immunofluorescence (DIF) in Michel medium shows linear C3 ± IgG along the basement membrane — the gold standard. Serology: anti-BP180 (NC16A) antibodies are the most sensitive and are used to track disease activity; anti-BP230 antibodies are adjunctive.

Treatment (specialist-led): Joly et al. NEJM 2002 established that topical superpotent corticosteroid (clobetasol propionate 0.05%, 30–40 g/day to the whole body) is first-line for localised to moderate disease — equivalent efficacy to oral prednisolone with significantly lower mortality in elderly patients. Oral prednisolone 0.5–0.75 mg/kg/day is used for severe or extensive disease. Doxycycline 200 mg/day plus nicotinamide 500 mg three times daily is a reasonable alternative for mild-to-moderate disease in patients unable to tolerate corticosteroids. Refractory cases: methotrexate, azathioprine, mycophenolate, rituximab, or IVIG under specialist direction. Emerging: dupilumab (off-label, not currently PBS-listed for BP).

Pemphigus vulgaris

Pemphigus vulgaris affects a younger cohort (peak age 40–60) and has higher mortality — historically 30–90% untreated; currently approximately 5–10% with modern treatment. Populations of Jewish, Mediterranean, South Asian, and Iranian ancestry have higher prevalence due to HLA associations.

Clinical: mucosal erosions (oral especially) typically precede skin involvement — sometimes for months, during which the diagnosis is missed. Skin bullae are flaccid and rupture rapidly to leave painful, slow-healing erosions. Nikolsky sign is positive — lateral pressure on normal-appearing skin produces extension of the erosion.

Diagnosis: perilesional DIF shows intercellular IgG and C3 (“chicken wire” pattern) within the epidermis. Serology: anti-desmoglein 3 (mucosal-dominant disease) ± anti-desmoglein 1 (mucocutaneous disease).

Treatment: Joly et al. NEJM 2017 (RITUX 3 trial) established rituximab (two doses 1,000 mg, two weeks apart, repeated at months 6 and 12) plus short-course prednisolone as first-line for moderate-to-severe pemphigus — complete remission in approximately 90% at 24 months versus 28% with prednisolone monotherapy. Rituximab is PBS Authority-listed for pemphigus vulgaris in Australia.

Dermatitis herpetiformis

Dermatitis herpetiformis is the cutaneous manifestation of coeliac disease, not a separate autoimmune blistering disease in the usual sense. It presents as intensely pruritic, symmetrical, herpetiform (grouped) vesicles on extensor surfaces — elbows, knees, buttocks, scalp, and shoulders. Vesicles are commonly excoriated before the patient is seen, leaving only excoriations and crust.

Diagnosis: perilesional DIF shows granular IgA deposits in the dermal papillae. Coeliac serology (anti-tTG IgA, anti-EMA) and small-bowel biopsy confirm the underlying coeliac disease.

Treatment: strict lifelong gluten-free diet is the only curative intervention, resolving both skin and intestinal disease over months to years. Dapsone 25–100 mg/day provides rapid pruritus relief while dietary response is awaited — G6PD testing is required before starting; monitor for methaemoglobinaemia and haemolysis. Refer to gastroenterology for coeliac confirmation and to a dietitian with coeliac expertise for dietary management, coordinating with Coeliac Australia.

Linear IgA disease and drug triggers

Linear IgA disease is characterised by the “string of pearls” annular blistering pattern — vesicles arranged around an urticarial central plaque. Vancomycin is the classic drug trigger and withdrawal typically resolves the eruption. Children are also affected (chronic bullous disease of childhood). DIF shows linear IgA at the basement membrane.

B. Evidence highlights

The Joly NEJM 2002 RCT remains the landmark trial that changed BP management: topical clobetasol comparable to oral prednisolone for disease control, with lower four-year mortality in elderly patients — the basis for the eTG and BAD 2022 recommendation for topical-first approach. The RITUX 3 NEJM 2017 RCT transformed pemphigus management — rituximab is now first-line for moderate-to-severe disease internationally and is PBS-listed in Australia.

Do not reflexively prescribe oral prednisolone first-line for localised bullous pemphigoid — the mortality data in elderly patients favours topical clobetasol. Do not use empirical antibiotics for blistering eruptions without microbiological evidence of secondary infection. Always review the full medication list before attributing a blistering eruption to a primary autoimmune cause — drug-induced AIBD resolves with withdrawal.

C. Australian operations — MBS and access

MBS items for the workup and management pathway:

• Standard GP consultations 23, 36, 44
• Punch biopsy of skin item 30068 — bill once per procedure for the lesional biopsy; the perilesional biopsy is a second unit
• Pathology: autoimmune serology and immunofluorescence [item 73881]; FBC, U&E, LFTs [item 73807]
• Consultant physician (dermatology, immunology) initial and subsequent items 132 and 133
• ATSI Health Assessment [item 715]; 75+ Health Assessment [item 707]
• GP Chronic Condition Management Plan 965/967 for ongoing shared care

PBS prescribing highlights:

• Topical clobetasol propionate 0.05% (Dermovate) — General Schedule
• Oral prednisolone — General Schedule
• Doxycycline — General Schedule
• Methotrexate, azathioprine, mycophenolate — Authority Required
• Rituximab — Authority Required for pemphigus vulgaris (specific PBS criteria)
• Dapsone — Authority Required
• IVIG — Authority Required for specified indications
• Dupilumab — not PBS-listed for BP (approved for severe atopic dermatitis only)

Australian patient resources: Australasian Blistering Diseases Foundation (ABDF) is the primary AU patient organisation and provides disease-specific information and peer support for BP, pemphigus, and DH. International Pemphigus and Pemphigoid Foundation (IPPF) provides international resources. Coeliac Australia supports patients with DH and coeliac disease.

Shared care after specialist initiation: the GP role includes monitoring for corticosteroid adverse effects (blood pressure, blood glucose, bone density — bisphosphonate prophylaxis for prolonged steroid use), ensuring TB and hepatitis B/C/HIV screening before immunosuppression, Pneumocystis jirovecii pneumonia prophylaxis with trimethoprim-sulfamethoxazole 480 mg daily when prednisolone is above 20 mg for more than four weeks, and vaccination (influenza, pneumococcal, COVID-19, non-live Shingrix pre-treatment). Monitor rituximab patients for opportunistic infection and hold live vaccines during immunosuppression.

D. Special populations

Elderly patients. BP is predominantly a disease of frailty. The GP must balance the need for treatment (which typically requires systemic or extensive topical immunosuppression) against the high risk of adverse effects in patients with multiple comorbidities. Doxycycline plus nicotinamide is an attractive steroid-sparing option in mild-to-moderate BP in a frail octogenarian. Careful monitoring for secondary skin infection, glycaemic disturbance on steroids, and falls risk is essential.

Pregnancy. Pemphigoid gestationis presents in late pregnancy or the postpartum period, typically with periumbilical urticarial lesions progressing to bullae. It is associated with anti-BP180 antibodies and carries a small but real risk of preterm delivery and small-for-gestational-age outcomes. Refer urgently to obstetric and dermatology services. Topical corticosteroids with careful obstetric monitoring are first-line; oral prednisolone for severe disease with specialist guidance.

Oncology patients on checkpoint inhibitors. Dermatitis and BP secondary to PD-1/PD-L1 inhibitors is increasingly common in GP shared-care of oncology patients. Coordinate management with the treating oncologist before withdrawing the immunotherapy agent, as discontinuation has cancer-treatment implications.

Patients of South Asian, Middle Eastern, or Jewish ancestry. Pemphigus vulgaris has higher prevalence in these groups due to HLA associations. A clinical presentation of chronic oral erosions in a 40–60-year-old from these backgrounds warrants pemphigus in the differential.

When to escalate

Refer urgently to dermatology for any suspected autoimmune blistering disease. The specific urgency levels:

• Suspected pemphigus (mucosal erosions, flaccid bullae, Nikolsky positive) — urgent, within days
• Elderly patient with intractable pruritus plus urticarial or early blistering eruption — semi-urgent, within one to two weeks for BP workup
• Pregnancy with new blistering — urgent combined obstetric and dermatology review
• Children with persistent blistering — urgent paediatric dermatology

Refer to the emergency department immediately for any suspected Stevens-Johnson syndrome or toxic epidermal necrolysis: extensive mucositis, skin detachment, systemic unwell.

Other specialist referrals: ophthalmology for mucous membrane pemphigoid with eye involvement (corneal scarring risk); oral medicine or dentistry for mucosal pemphigus; gastroenterology for DH coeliac confirmation; ICU or burns unit for SJS/TEN.

What this article is and is not

This is general health information drawn from current Australian dermatology guidelines — Therapeutic Guidelines (eTG), RACGP dermatology resources, Australasian College of Dermatologists, ABDF — and landmark AIBD trials. It is not personal medical advice and does not create a doctor–patient relationship. Diagnosis and treatment of autoimmune blistering diseases requires specialist dermatology input; decisions about biologic therapy and immunosuppression are made jointly with the treating dermatologist.

For Australian patient information: ABDF, DermNet NZ, HealthDirect, Coeliac Australia.

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Sources cited

1. Joly P et al. — Oral vs topical corticosteroids in bullous pemphigoid. New England Journal of Medicine 2002
2. Joly P et al. — Rituximab for pemphigus (RITUX 3 trial). New England Journal of Medicine 2017
3. Australasian Blistering Diseases Foundation (ABDF)
4. Australasian College of Dermatologists — clinical position statements
5. Therapeutic Guidelines (eTG complete) — Dermatology
6. RACGP — Dermatology clinical resources
7. British Association of Dermatologists — Bullous Pemphigoid Guidelines 2022
8. Cochrane — Interventions for bullous pemphigoid
9. NICE Clinical Knowledge Summary — Pemphigoid
10. International Pemphigus and Pemphigoid Foundation (IPPF)
11. DermNet NZ — Bullous diseases
12. Coeliac Australia
13. MBS item 30068 — Punch biopsy of skin
14. MBS item 132 — Consultant physician initial assessment
15. MBS item 965 — GP Chronic Condition Management Plan preparation